By way of background in the process of electrostatographic reproduction, a light image of an original to be copied or printed is typically recorded in the form of a latent electrostatic image upon a photosensitive member with a subsequent rendering of the latent image visible by the application of electroscopic marking particles commonly referred to as toner. The visual toner image can be either fixed directly upon the photosensitive member or transferred from the member to another support medium such as a sheet of plain paper. To render this toner image permanent, the image must be “fixed” or “fused” to the paper, generally by the application of heat and pressure.
With the advent of high speed monochrome and color marking machines, including xerography reproduction machines wherein copiers or printers can produce at a rate in excess of three thousand copies per hour, the need for an improved cleaning system designed to collect airborne toner from the developer housing or station is evident.
Many xerographic copiers and duplicators use a waste system designed to collect waste toner from the developer housings and the cleaner. Other important functions of the contamination control system include, transport, separation, collecting and filtering of the air before it is returned to an environmental unit, or in many cases the customer environment. Another function of the contamination control system is the collection, transport, and processing of ozone generated by the corona devices. The flow requirements of the each of these systems are such that a variety of blowers are needed to provide the required air flow. There are two ways that system performance may be degraded. First is the increased resistance in the systems due to the filling of the filters, and operation at different altitudes.
During normal operation, either at sea level or altitude, the performance of the contamination control system will degrade over time due to the increased filter resistance. It is required in many cases in the prior art to overdesign the system so that performance is maintained after a specified number of prints between maintenance cycles. This practice produces, in many cases, excessive noise from the blowers, and excessive toner waste from the developer housings. This invention proposes the use of a blower control circuit, a temperature sensor, and a mass flow rate sensor to adjust the blower speed as the flow is reduced due to normal machine use.